Many existing matrix display devices, for example, Thin-Film-Transistor (TFT) displays having RAM-less driver Integrated Circuits (ICs), operate on 4 control signals: vertical synchronization (Vsync); horizontal synchronization (Hsync); pixel clock (Dotclk); and data output enable (OE) signals. The Vsync signal or other signal controls each frame. The Hsync signal or other signal controls each line. The Dotclk signal or other signal controls each pixel. And the data OE signal or other signal determines whether the input data is valid or invalid. Data are written when the OE signal is active in synchronization with the Vsync, Hsync and Dotclk signals.
Prior Art FIG. 1 illustrates timing waveforms for a conventional 4×4 matrix TFT display active at 60 frames per second (fps). In the Vertical Timing waveform, the Vsync pulse indicates the start of a new frame. Within each frame, there are four Hsync pulses corresponding to each of the four horizontal rows. In the Horizontal Timing waveform, the Hsync pulse indicates the start of a new row. Within each row, there are four Dotclk signals corresponding to each of the four pixels in each row. The OE signal, which is active when high, indicates that the input is valid display data.
It is known generally to activate only portions of the display by adjusting the OE timing signal so that a portion of the display is inactive. In Prior Art FIG. 2, the OE timing signal is active on only horizontal rows 2 and 3 of the display, but not on rows 1 and 4 of the display where in rows 1 and 4 are inactive. The active portion of the display may start from any row, depending on when the OE signal in the Vertical Timing axis is active. The partial screen size may vary from one row to full screen depending on the duration of the OE active pulse. Areas of the display where the OE signal is inactive are non-display areas where images are not shown.
The various aspects, features and advantages of the disclosure will become more fully apparent to those having ordinary skill in the art upon careful consideration of the following Detailed Description thereof with the accompanying drawings described below.